Cathode Coating Resistance Balance for Low-Gas Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries with solid electrolyte coatings face increased resistance and reduced gas suppression due to thick coatings, leading to quality dispersion and yield issues.
Innovation Solution
A positive electrode composite active substance with a thin lithium ion conductive coating layer, having a grain boundary resistance 3 to 20 times larger than the charge transfer resistance, is used to suppress gas generation and resistance loss, while improving yield and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thick solid electrolyte coating layer is applied to the positive electrode active substance surface, then gas generation from electrolyte decomposition is suppressed, but resistance loss increases due to the coating layer
Solution Approach 1:
The invention optimizes the thickness parameter of the solid electrolyte coating layer to a specific range (5-50 nm) that balances gas suppression and resistance characteristics. This parameter optimization resolves the contradiction by finding the optimal thickness value that provides sufficient protection against electrolyte decomposition while maintaining low resistance.
Solution Approach 2:
The invention uses a composite structure consisting of the positive electrode active substance (such as LNMO) combined with a solid electrolyte coating layer. This composite material approach allows the system to benefit from both the high voltage performance of the active substance and the protective properties of the coating, while the coating thickness is controlled to minimize resistance impact.
2Loss of energy
If the solid electrolyte coating thickness is reduced, then resistance loss is decreased, but gas generation suppression effect is weakened
Solution Approach 1:
The invention establishes a lower bound for the coating thickness parameter (5 nm) that ensures sufficient gas suppression while avoiding excessive resistance. This parameter specification resolves the contradiction by defining the minimum thickness needed for effective protection without compromising electrical performance.
Solution Approach 2:
The solid electrolyte coating layer acts as an intermediary between the positive electrode active substance and the liquid electrolyte. This intermediate layer provides a protective function that suppresses direct contact and decomposition reactions, while its optimized thickness ensures that the resistance impact remains acceptable.
3Object-affected harmful factors
If a solid electrolyte coating is applied to suppress gas generation, then electrolyte decomposition is reduced, but quality dispersion and yield issues occur in production
Solution Approach 1:
The invention specifies precise parameter ranges for the coating layer (thickness: 5-50 nm, grain boundary resistance ratio: 3-20 times) that ensure consistent performance and manufacturability. These parameter specifications enable reliable mass production with reduced quality dispersion while maintaining effective gas suppression.
Solution Approach 2:
The invention uses grain boundary resistance measurement as a feedback parameter to control and quality-assure the coating layer. By monitoring the grain boundary resistance ratio, the manufacturing process can be adjusted to maintain consistent coating quality, thereby improving yield and reducing variability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces resistance loss and gas generation from electrolyte decomposition, enhancing the performance and production quality of lithium ion secondary batteries.
Implementation Method 1
the coating layer has lithium ion conductivity
Implementation Method 2
a coating layer covers a surface of an oxide active substance... suppress the generation of gas due to the decomposition of the nonaqueous electrolyte solution
Data Source
AI summary
The present invention provides a positive electrode composite active substance and a lithium ion secondary battery in which a coating layer covers a surface of an oxide active substance, and a resistance loss due to the coating layer can be suppressed while generation of gas due to decomposition of a nonaqueous electrolyte solution is suppressed as compared with a conventional case. A positive electrode composite active substance constituting a part of a positive electrode of a lithium ion secondary battery using a nonaqueous electrolyte solution as an electrolyte, the positive electrode composite active substance including: an oxide active substance; and a coating layer covering a surface of the oxide active substance, in which the coating layer has lithium ion conductivity, and a grain boundary resistance of the coating layer is 3 times or more and 20 times or less larger than a charge transfer resistance of the oxide active substance.